Multi-injection molded flange with gasket in wedge shaped opening

ABSTRACT

In the present invention, when a multi-injection molded body made of at least a first and a second resins is molded, catching means are formed generally by pressing a part of the surface about an opening of a concave section formed in a first molded body made of the first resin to project interior side wall faces of the concave section inward, and injecting a second resin to mold a second molded body thus formed has catching means in the concave section, so that the second molded body is tightly fixed to the first molded body.

This application is a continuation of application Ser. No. 07/347,908,filed May 5, 1989 now abandoned.

FIELD OF THE INVENTION

The present invention relates to a multi-injection molded body, a methodof molding for the same, and a multi-injection molding machine. Moreprecisely it relates to a multi-injection molded body consisting of twoor more kinds of resins, a method of molding for the same, and amulti-injection molding machine for the same.

BACKGROUND OF THE INVENTION

Recently, cars, home electric appliances, cameras, containers, etc. havebeen required to become lighter in weight. As such, parts in machines,appliances, etc. have been changed from metals to plastics.

Parts made of plastics consist of a plurality of molded bodies(described as first molded body or bodies in the following description),and sealing parts (described as second molded body or bodies in thefollowing description). Sealing parts are made of such elastic polymersas silicon gum, urethane gum, styrene-butadiene gum, etc., and are usedin assembling sections between parts made of plastics so as to providesealing, absorbing or nonskid capabilities for products manufacturedtherewith.

Conventionally, the second molded bodies are independently molded fromthe first molded bodies, then they are manually assembled into the firstmolded bodies. In such a method, there are disadvantages of lowerassembling precision and increasing assembling steps. To solve thesedisadvantages, there was disclosed a method of multi-injection moldingin Japanese Provisional Publication (Kokai) Gazette 60-52322 andJapanese Provisional Publication (Kokai) Gazette 63-104809. The methodcomprises the steps of molding a first molded body having a concavesection on the surface thereof by injection molding, and injectingelastic polymer for forming a second molded body in the concave section.In this conventional method, multi-injection molded bodies consisting ofthe first molded body and the second molded body are molded in oneinjection molding step, so that assembling precision can be increased,and assembling steps can be reduced.

In the above conventional method, first molded bodies are molded byinjection molding, and the walls of concave sections are formedapproximately vertical from the bottom faces thereof, in order that onecan pick products out from molding machines easily. But in the abovemethod, second molded bodies, molded in concave sections of first moldedbodies, can also be pulled out of the first molded bodies easily becausethere are provided no catching means on the side wall faces of theconcave sections. In order to fix second molded bodies in concavesections of first molded bodies, as disclosed in the gazett No.63-104809, reactive elastomer layers, primer layers, etc. are formedbetween inner bottom faces of concave sections of first molded bodiesand bottom faces of second molded bodies to adhere them.

OBJECT AND SUMMARY OF THE INVENTION

The object of present invention is to provide multi-injection moldedbodies, which consist of a first and a second molded body molded byinjection molding, and whose second molded bodies are tightly fixed inconcave sections of said first molded bodies without adhering layers. Amethod of molding for the same; and a multi-injection molding machinefor molding the same are also provided.

We have found that catching (or holding) means can be formed on the sidewall faces of the concave sections of the first molded body by the stepsof forming an undercut section, by pressing upon the rim, or interiorwalls to the concave section, to project the rim area of the side wallstowards the inside of the concave section, and then injecting a resinmelt for forming the second molded body into the concave section of thefirst molded body, so that the second molded body can be tightly fixedto the first molded body.

The present invention provides that, in a multi-injection molded bodyformed by at least two kinds of resin such as a first resin and a secondresin, and comprising a first molded body A made of the first resin, anda second molded body B made of the second resin, and the multi-injectionmolded body being characterized in that at least a part of a concavesection 3, which is formed on a joint face of the first molded body Ajoining the second molded body B, is projected toward the inside of saidconcave section 3 to form an undercut section, and the second resin isfilled in the concave section 3 forming a part of the second molded bodyB.

The present invention further provides a multi-injection molding methodto mold a multi-injection molded body formed by at least two kinds ofresin, such as a first resin, and a second resin and comprising a firstmolded body A made of the first resin and a second molded body B made ofthe second resin characterized in that molding the first molded body Ahas a concave section 13 on the joint face thereof joining to the secondmolded body B, an undercut section is formed by pressing at least a partof the rim of the concave section 13 to project the walls of the concavesection 13 toward the inside thereof to form an undercut section 5, thenthe section resin melt is injected into the concave section 3 and acavity 7 of a mold Y or Y'.

And the present invention further more provides an injection moldingmachine for a multi-injection molded body formed by at least two kindsof resin, such as a first resin and a second resin, and comprising afirst molded body A made of the first resin, and a second molded body Bmade of the second resin and being characterized in that a pair of firstmolds Z and W for molding the first molded body A have a concave section13 on the joint face thereof joining to the second molded body B, and asecond mold Y has a pressing section for pressing at least a part of thearea about the rim of the concave section 13 of the first molded body Ato project the side walls of the concave section 13 toward the insidethereof to form an undercut section 5, a pair of third molds Y or Y' andZ for injecting the second resin melt in a cavity 7, which accommodatesthe first molded body A and which molds the second molded body B,including the concave section 3 of the first molded body A.

The method of the present invention, further provides for forming theundercut section 5 in the concave section 3 of the first molded body A.Such can be easily achieved pressing the area about the rim of theconcave section 13 of body A with projected sections 6 of a second moldY, or by pressing a projected section 9 previously formed in thevicinity of the concave section 13, or by pressing at least a part ofwalls exterior to the concave section 13. Additionally, if injection ofthe second resin melt for molding the second molded body B is executedwith presssing all parts of the rims of the concave section 3, flasheseasily formed in the vicinity of the second molded body B areeffectively prevented even in cases where the second resin is a materialwith small surface tension, such as silicon gum, etc.

In the injection molding machine of the present invention, if thepressing sections of the mold Y are formed as projecting sections 6, orare capable of pressing at least a part of exterior walls to the concavesection 13, the undercut section 5 can be easily formed in the concavesection 3. For example, even in a pair of first molds Z and W (FIG. 7a)for molding the first molded body A, cavities to mold have projectingsections 9 in the vicinity of the concave section 13. If the projectingsections 9 of the first molded body A are pressed, the undercut sections5 can be easily formed in the concave section 13. In such a case, it isprefer to have one of a pair of molds Z and W, in which the first moldedbody A is left when the molds are opened, and then making common use ofthe mold Z by combining with a second Y (FIG. 7b) having a pressingsection to form the undercut section 5 in the concave section 3 of thefirst molded body A, or to a mold, which accomodates the first moldedbody A, and wherein a pair of molds forms the second molded body B. Itis also, especially preferred that the pressing sections for pressingall parts of rim of the concave section 13 are provided, such as in themold Y or Y' (FIG. 16) into which the second resin for molding the firstmolded body A is injected, since they are capable of pressing all partsof the rim of the concave section 3 while injecting the second resininto the concave section thereof, so that flashes easily formed duringmolding the second molded body B are effectively prevented.

The present invention is especially preferred in cases wherein the tworesins are noncompatible, and wherein the second resin is an elasticpolymer for providing sealing, absorbing, or nonskid properties, etc. tothe article produced.

Note that, the word "undercut section" as applied to concave section 3means at least a part whose width of space is narrower than the width ofthe bottom face of the concave section 3.

In the present invention, the undercut section 5 may be formed in theconcave section 3 by pressing about the surface of rim area of theconcave section opening of the first molded body A to form a catchingmeans for catching the second molded body B, then the second resin formolding the second molded body B is injected into the concave section 3,so that the second molded body B is tightly fixed in the concave section3 of the first molded body A. Alternatively the undercut section 5 ofthe concave section 3 of the first molded body A, may be easily formedby clamping a third mold Z, accommodating the first molded body A, and asecond mold Y having a pressing section for pressing in the vicinity ofthe opening of the concave section 13 of the first molded body A.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described by way of example andwith reference to the accompanying drawings, in which:

FIG. 1 shows a perspective view and a sectional view of an embodiment ofa multi-injection molded body of the present invention;

FIGS. 2-4 show explanation views which explain a method of moldingmulti-injection molded bodies of the present invention;

FIGS. 6-8 show explanation views which explain a multi-injection moldingmachine of the present invention;

FIGS. 9-16 show explanation views of certain other embodiments of thepresent invention; and

FIG. 17 shows a perspective view of another embodiment of amulti-injection molded body of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will now be explained with reference to drawings.

FIG. 1(a) shows a perspective view of an example of the multi-injectionmolded bodies of the present invention, and FIG. 1(b) shows a sectionalview of the multi-injection molded body of FIG. 1 taken along the lineX--X of FIG. 1(a).

In FIG. 1, in a flange section of a first molded body A which is made ofa first resin (e.g. nylon-6 including glass fiber), a seal ring as asecond molded body B made of a second resin (e.g. silicon gum) isprovided and a plurality of through-holes 10 are bored therein.

There is formed a concave section 3 on the joint face of the firstmolded body A joining to the second molded body B. The upper section ofthe walls of the concave section 3 is narrower than the lower sectionthereof, so the sectional shape of the concave section 3, as shown inFIG. 1(b), is a so called "inverted-tapered shape" wherein the width ofthe opening 4 of the concave section 3 is about the narrowest; andwherein the width of the bottom section of the concave section 3 isabout the widest. Therefore, the section 5 is formed as the undercutsection. In the concave section 3, silicon gum as the second resin isfilled therein, and the second resin forms a part of the second moldedbody B. Therefore, a part of the second molded body is attached in theconcave section 3 having the undercut section in the bottom section 5,so the projected section of the opening 4 of the concave section 3 isformed as catching means to catch the second molded body B, so that thesecond molded body B is tightly fixed in the concave section 3 by theundercut section.

The multi-injection molded body A is molded by the method shown in FIG.2.

Namely, first, the first molded body A having the concave section 13 isleft in a mold Z of a pair of molds for molding the first molded body A[see FIG. 2(a)]. The concave section 13 of the first molded body A isopened on the upper face thereof. The sectional shape of the concavesection 13 is, as shown in FIG. 2(a), a rectangle and its side walls areformed approximately vertical to the inner bottom face of the concavesection 13, so that another mold, which molds the first molded body Awith the mold Z, can easily leave from the first molded body A duringmold opening, so that then the first molded body A can be left in themold Z.

Next, a surface area about the rims of the first molded body A ispressed by clamping a mold Y, which has projecting sections 6 and acavity 7 for molding the second molded body, and the mold Z in which thefirst molded body A has been left therein [FIG. 2(a), (b)].

Both side walls of the concave section 13 are projected inward. Thelength of the projection is, as shown by numeral 8 in FIG. 2(b), thatthe width of the upper section is longer than the width of the lowersection, so that sectional view of the concave section transforms intoan inverted-tapered shape. In such a way an undercut section is formedin the vicinity of the bottom section 5 of the transformed concavesection 3, so that a catching (or holding) means is formed at opening 4of the concave section 3.

Next, the second resin is injected into the concave section 3 and thecavity 7 of the mold Y, and then the molds Y and Z are opened to obtaina multi-injection molded body consisting of the first molded body A andthe second molded body B which is tightly fixed to molded body A by theconcave section 3 [FIG. 2(b), (c)].

Appropriate second resins for molding the second molded body B may havea low surface tension, e.g. silicone gum.

There is also a disadvantage that, however, when the second resin haslow suface tension, since they can enter quite narrow gaps (e.g. 5μ),thereby easily forming flashes around the second molded body B.

In this embodiment, sealing ability around the concave section 3 can begreatly increased by pressing all parts of the rim of the concavesection of the first molded body A with the projecting sections 6 of themold Y during injecting the second resin into the concave section 3 andthe cavity 7, so that forming flashes around the second molded body Bcan be prevented.

The undercut section can be formed by another method, as shown in FIG.3.

First, projecting sections 9 are previously formed in the vicinity ofthe opening of concave section 13 [FIG. 3(a)]. The concave sections 9are pressed by the bottom face of a mold Y having a cavity 7 for moldingthe second molded body [FIG. 3(a), (b)]. In this method, the pressedmark on the upper face of the first molded body A can be smaller thanthe method of pressing by the projecting sections 6 of the mold Y shownin FIG. 2 [FIG. 3(b), (c)].

The methods shown in FIGS. 2 and 3 can be combined. This embodiment isshown in FIGS. 4 and 5.

FIG. 4 shows the method of doubly pressing the rim of the opening ofconcave section 13 of the first molded body A and the projectingsections 9, which is previously formed in the vicinity of the opening ofthe concave section 13. While, FIG. 5 shows the method of pressing eachside of the opening of the concave section 13. In the above statedmethods, the projecting length of the wall of the concave section 13 ofthe method shown in FIG. 5 can be the longest among them. Note that, inabove stated embodiments, the sectional shape of the concave section 13has been a rectangle, but the same is not necessary if the mold, whichmolds the first molded body A, can be easily removed from the firstmolded body A, and thus the sectional shape of the concave section 13may be drawable-tapered shape, half circle, half ellipse, etc.

Additionally, the sectional shape of the projecting section 6 of themold Y may be wedge shape, half circle, half ellipse, trapozoid, etc.The projecting section 6 and/or 9 may be provided around the rim of theconcave section 13 of the first molded body A to press all of the rim,but also may be provided to only press a part of the rim of the concavesection 13. Either way, the projections are required to press in thevicinity of the opening of the concave section of the first molded bodyA to project the walls of the concave section inward. If the mold Y cantightly contact the first molded body A, which is left in the mold Z,except for the concave section, the walls of the concave section can beeasily projected inward during clamping the molds Y and Z so as to pressthe rim of the concave section 13 of the first molded body A, and thusform an undercut section. The mold Y, as shown in FIG. 6, may have aninjection hole 11, through which the second resin for molding the secondmolded body B is injected in the cavity 7. Note that, the injection hole11 may be provided in a mold apart from the mold Y.

FIG. 6 shows a multi-injection molding machine for molding themulti-injection molded bodies of the present invention.

The injection molding machine shown in FIG. 6 has a first injectiondevice 20 and a second injection device 21 on a base 30. Molds W, Y andZ are provided between a movable board 24 and a fixed board 22. The moldZ is fixed with bolts on the movable board 24 which is moved by aclamping piston 26 slidably attached in a clamping cylinder 27. The moldZ can be closed, clamped or opened with the mold W or Y which are fixedwith bolts on a slide board 25. The slide board 25 is slid by an oilcylinder 23 which is provided on the fixed board 22. The board can slidebetween the position where the mold Z is closed or clamped with the moldW, and the position where the mold Z is closed or clamped with the moldY.

In the injection molding machine shown in FIG. 6, after the molds Z andW were clamped by moving the movable board 24 toward the right with themovement of the clamping piston 26, the first injection device 20advances, and nylon-6 melt including glass fiber is injected into acavity, which is formed by the molds Z and W, for molding the firstmolded body.

Pellets of nylon-6 including glass fiber, which are provided through ahopper 29 mounted on the first injection device 20, are melt in thefirst injection device 20.

After solidification of the injected nylon-6 and moving back of thefirst injection device 20, the movable board 24 is moved to the left toopen the molds Z and W. During mold opening, the concave section 13 ofthe first molded body A opens on the upper face thereof, and the firstmolded body A is left in the mold Z.

Next, the first molded body A left in the mold Z, as shown in FIG. 6(b),is closed and clamped to the mold Y moved with sliding of the slideboard 25. As shown in FIG. 6(a), there are provided the projectingsections 6 around the cavity 7 for molding the second molded body,additionally the injection hole 11 for injecting a second resin such assilicon gum is connected to the cavity 7. There is provided a concavesection 40 in approximately center of the mold Y. As shown in FIG. 6(b),the concave section 40 can accommodate a sprue 33 formed on the firstmolded body A during closing the molds Z and Y. Note that, the sprue 33is the solidified first resin filled in a resin path 133 connecting thefront end of the nozzle of the first injection device to the cavity formolding the first molded body.

The projecting sections 6 of the mold Y press the rim of the concavesection of the first molded body A, to transform the concave section 13into the concave section 3 whose sectional shape is an inverted-taperedshape. The second injection device 21 is advanced and a second resinsuch as silicon gum is injected into the concave section 3 and thecavity 7 to mold the second molded body B.

Silicon gum may be provided from a pot 31 of a seal supplyer 28 to thesecond injection device 21, and hardening agents may also be providedfrom a pot 32 thereof to the second injection device 21. Both are mixedin the second injection device 21 and injected into the concave section3 and the cavity 7. The second resin injected is solidified in theconcave section 3 and the cavity 7. The second resin is generally athermosetting resin, so that cooling the second injection device 21 andheating the temperature of the mold Y about 120°-150° C. are capable ofimmediate solidification of the second resin in the concave section 3and the cavity 7 without solidification in the second injection device21. Within the above temperature range for the mold Y, such temperaturesdo not affect the choice of nylon-6 as a first thermoplastic resin,since the mold W for molding the first molded body A is preferably keptat a temperature of about 80°-90° C. to immediately solidify the firstresin.

In the injection machine shown in FIG. 6(b), the rim of the concavesection 13 of the first molded body A is pressed by the projectingsection 6 of the mold Y, FIG. 7 shows another embodiment. The machineshown in FIG. 7 is, as same as the machine shown in FIG. 6, but in themachine, the mold Z and nozzles 120 and 121 can move horizontally duringmold clamping and mold opening. Note that, their movement are shown asup and down in FIG. 7 but they can also move in a horizontal direction.As shown in FIG. 7(a), the first resin melt is injected into the cavityfor molding the first molded body formed by the molds Z and W from thenozzle 120 of the first injection device 20, so that the projectingsections 9 and formed in the vicinity of the rim of the concave section13 of the first molded body A.

Next, after opening molds W and Z, the mold Z in which the first moldedbody A (having the projecting sections 9) has been left and the mold Y(which has moved by sliding the slide board 25) are clamped, so that theprojecting sections 9 of the first molded body A are pressed by thebottom face of the mold Y. At such a point, the sectional shape of theconcave section 13 is transformed into the inverted-tapered shape toform the concave section 3 having an undercut section. Then the secondresin is injected into the concave section 3 and the cavity for moldingthe second molded body B. The second resin is injected via the nozzle121 of the second injection device 21 and the injection hole 11 [FIG.7(b)]. The mold Y has, as shown in FIG. 7(b), the concave section 40accommodating the sprue 33 formed on the first molded body A, so thatclamping the molds Z and Y can be executed without cutting the sprue 33.

In the machine shown in FIG. 6, the molds W and Y are respectively fixedwith bolts on the slide board 25, the molds W and Y may, however, alsobe in one body, that single body also having a base connecting the twomolds. Note that, the slide board 25 can be substituted a rotatingverses sliding board. The rotary board 25 being rotated to travel themolds W and Y to a position for closing with and being clamped with themold Z.

In the above described embodiments, both sides of the rim of the concavesection 13 on the upper face of the first molded body A are pressed totransform the sectional shape. If at least one of walls of the concavesection 13 is thin, it may be impossible to transform the sectionalshape of the concave section 13 by pressing upon both sides of its rim.In that case, the following methods are adaptable.

Embodiments shown in FIGS. 9 and 10 are the case where one of the sides(numeral 50 in FIG. 9) of the concave section 13 is thin, so that areais unable to press upon the one of the sides thereof. In this case, itis possible to press the upper surface of the side 51 to form theundercut section in the concave section 31. In FIG. 10, the face 52,which contacts the thin side 50, is inclined to press the side towardthe side 51, while the upper-surface of the side 51 is pressed by theprojecting section 6 of the mold Y, so that the concave section 13 canbe trans formed into an inverted-tapered shape.

The method shown in FIG. 9 can be applied, as shown in FIG. 11, to molda cap 100 having a seal 220 on the inner bottom face thereof. Namely, itis impossible to press the upper faces of thin sides 50 and 51 of theconcave section 13 of the first molded body but it is possible to formthe concave section 3 having the undercut section by pressing theupper-surface of one of sides 110 of the concave section 13. The methodshown in FIG. 10 can also be applied, as shown in FIG. 12, to form theconcave section 3 having the undercut section by pressing the uppersections of the sides 50 and 51 inward by a curved face 52 of the moldY.

The embodiments shown in FIGS. 13 and 14 are methods for molding thesecond molded body B between an inner pipe and a outer pipe of a doublepipe. If the part of the inner pipe can be transformed, as shown in FIG.13, it is possible to form concave section 3 having the undercut sectionby transforming the part of the inner pipe outwards and thereforetowards the inside of the concave section 13, by a tapered bottomsection 56 of a rod-like projecting section 55 of the mold Y. And if itis impossible to transform the inner pipe, as shown in FIG. 13, it ispossible to form the concave section 3 having an undercut section bytransforming the exterior wall of the part of an outer pipe toward theinside of the concave section by a projecting pin 57 of the mold Y asshown in FIG. 14.

Furthermore, method combining the methods of FIGS. 13 and 14 is shown inFIG. 15. In this method, an undercut section can be formed in theconcave section 3, and forming flashes can be prevented during moldingthe second molded body. Note that, in case of pressing at least one ofsides of the concave section 13, it is allowable to press all part ofrims or a part thereof.

In an embodiment of the present invention as shown in FIG. 16, theconcave section of the first molded body A consists of a wide groove 130and a narrow groove 13 as a double groove. In this case, the resin formolding the second molded body is injected into the wide groove 130 andthe concave section 3 after forming the concave section 3 having theundercut section by the rims of the narrow groove 13. This method can beachieved by providing the injection hole 11 (see FIG. 6) in a mold Y'apart from the mold Y. Namely, it means that an additional mold Y'having the injection hole 11 is provided besides the molds W, Y and Z.First, the first molded body A having the concave section like a doublegroove, as shown in FIG. 16(a) is molded with the molds W and Z. Next,as shown in FIG. 16(b), the undercut section is formed by pressing uponboth sides of the rim of the narrow groove 13 of the first molded bodyA, which has been left in the mold Z, by the projecting sections 6 ofthe mold Y to project the side walls of the narrow groove 13 inward.Then the second resin is injected into the concave section and thecavity through an injection hole 11 of a mold Y', to mold the secondmolded body B as shown in FIG. 16(b) after the closing the molds Y' andZ, so that the first and second molded bodies A and B can bemanufactured into one body.

In the above described embodiments, nylon-6 or another thermoplasticresin is used as the first resin for molding the first molded body A,and silicon gum or another thermosetting resin is used as the secondresin for molding the second molded body B, since many kinds of resinsare usable in the present invention. For example, polyester, polyvinylchloride, polyethylene, polypropylene, etc. can be used as thermoplasticresins, and epoxy resin, unsaturated polyester, etc. can be used asthermosetting resins. Combinations of the first and second resins arenot limited, however, to thermosetting resins and thermoplastic resins.For example, one may use different thermoplastic resins as both thefirst and second resin. Additionally, mutually non-compatible resins(e.g. polyester and polypropylen) can be used to mold themulti-injection molded bodies provided herein.

In the present invention, it is possible to fix a sealing material asthe second molded body B, such molded body B made of an elastic polymertightly attached to a complex first molded body A as shown in FIG. 17 byinjection molding. The second molded body B shown in the FIG. 17 may beused as a sealing material, an absorbing material or a nonskid materialbecause of its elasticity.

Different and preferred kinds of elastic polymer, of course, can be usedwith regard to different types of anticipated uses.

In this embodiment (FIG. 17), the injection molding machine is a sidestroke type whose movable board 24 moves in the horizontal direction,but the present invention can be applied to a vertical stroke typemachine whose movable board moves in the vertical direction.

In the present invention, it is easy to mold a multi-injection moldedbody whose second molded body (e.g. sealing, absorbing or nonskidmaterial, etc.) is tightly fixed to a complex shaped first molded bodyby injection molding while preventing the fomation of flashes.Therefore, the step of manually assembling the sealing material, etc. tothe first molded body and the step of de-flashing can be reduced duringthe molding process.

What is claimed is:
 1. An injected molded body consisting essentially ofa first resin; the molded body having a concave section therein, theconcave section having an opening which forms on a surface of the moldedbody, wherein the opening of said concave section forms a ring having aninner and outer fringe, the concave section having sidewalls whereinparts of the sidewalls of the concave section are projected inward toform undercut sections in the concave section, the concave sectionhaving a bottom; and the molded body having depressed push-marks, thepush-marks being formed on a surface of said molded body continuouslyabout the opening of said concave section, wherein a push-mark is formedalong both the inner and outer fringes of the opening of said concavesection, whereby the formation of the depressed push-marks projectsparts of the sidewalls of said concave section inward, to give undercutsections in the concave section.
 2. The injection molded body accordingto claim 1, wherein said depressed push-marks are a groove.
 3. Theinjection molded body according to claim 2, wherein the transversecross-sectional shape of said grooved push-marks are a wedge.